Abstract
The influence of concentrate or feed blocks with or without Polyethylene glycol (PEG,
molecular weight 4000) on the carcass characteristics and weight of offal components
of 25 Barbarine
ram lambs offered Acacia cyanophylla Lindl. foliage was studied.
The animals were divided into
5 equal groups and housed in individual pens for 74 days.
All of the animals received 400 g oat hay
and air-dried foliage of acacia ad libitum.
Two groups were supplemented with 300 g concentrate
with (C
) orwithout
(C) 20 g PEG. The other groups had free access to urea-containing feed blocks
with
(BU
) or without (BU) PEG. One other treatment was a PEG-containing
feed block without
urea (B
). PEG was used to preferentially bind
A. cyanophylla condensed tannins (CT). At the end
of the growth trial,
the animals were slaughtered, offal components were weighed, left half carcasses
were dissected and carcass tissues were weighed. At slaughter, body weight (BW)
was the highest
(
P < 0.01) in the group receiving concentrate and PEG
(35.4 kg). The animals on diets C, B
and
BU
were slaughtered at similar BW (33.4, 31.8 and 32.1 kg, respectively) and those
on BU had the
lowest BW (27.8 kg). Dressing percentage was not affected by diet
treatments. The weights of the
head, feet, lungs, heart and abomasum were not affected
by the diet. The diet significantly influenced
the skin, testes, liver, kidneys and rumen
weights. The animals fed concentrate had heavier skin
(4485 g) and rumen (812 g) than
those fed blocks (3773 and 720 g for the skin and rumen, respectively).
The animals
receiving BU had the smallest organs. On contrasting treatments plus/minus
PEG, it was
observed that PEG administration significantly increased the weight of all organs.
PEG
supply significantly increased (
P < 0.01) testis weight (196 vs. 127 g with/without PEG).
Due to
treatment effects on slaughter BW and hence carcass weight, muscle, bone and fat
weights were
lower in the BU group compared to those in the other groups. In C,
C
, B
and BU
groups,
there was no significant
difference in body muscle weight. Indeed, the animals fed A. cyanophylla
with feed
blocks with PEG and without urea (B
group) produced the same amount
of muscle as
those produced with PEG and urea-containing feed blocks or conventional
diets (concentrate). The animals given feed blocks (more protein and less energy than
the concentrate) were less fat (20.0%) than those receiving concentrate (24.7%).
The use of acacia foliage and feed blocks without urea but containing PEG may be a
useful solution to produce lean lamb in a more economic manner.